<template>
  <div class="music-list">
    <div class="back" @click="back">
      <i class="icon-back"></i>
    </div>
    <h1 class="title" v-html="title"></h1>
    <div class="bg-image" :style="bgStyle" ref="bgImage">
      <div class="play-wrapper">
        <div ref="playBtn" v-show="songs.length>0" class="play" @click="random">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
      <div class="filter" ref="filter"></div>
    </div>
    <div class="bg-layer" ref="layer"></div>
    <scroll :data="songs" @scroll="scroll"
            :listen-scroll="listenScroll" :probe-type="probeType" class="list" ref="list">
      <div class="song-list-wrapper">
        <song-list :songs="songs" :rank="rank" @select="selectItem"></song-list>
      </div>
      <div v-show="!songs.length" class="loading-container">
        <loading></loading>
      </div>
    </scroll>
  </div>
</template>

<script type="text/ecmascript-6">
  import Scroll from '@/base/scroll/scroll'
  import Loading from '@/base/loading/loading'
  import SongList from '@/base/song-list/song-list'
  import {prefixStyle} from '@/common/js/dom'
  import {playlistMixin} from '@/common/js/mixin'
  import {mapActions} from 'vuex'

  const RESERVED_HEIGHT = 40
  const transform = prefixStyle('transform')
  const backdrop = prefixStyle('backdrop-filter')

  export default {
    mixins: [playlistMixin],
    props: {
      bgImage: {
        type: String,
        default: ''
      },
      songs: {
        type: Array,
        default: []
      },
      title: {
        type: String,
        default: ''
      },
      rank: {
        type: Boolean,
        default: false
      }
    },
    data() {
      return {
        scrollY: 0
      }
    },
    computed: {
      bgStyle() {
        return `background-image:url(${this.bgImage})`
      }
    },
    created() {
      this.probeType = 3
      this.listenScroll = true
    },
    mounted() {
      this.imageHeight = this.$refs.bgImage.clientHeight
      this.minTransalteY = -this.imageHeight + RESERVED_HEIGHT
      this.$refs.list.$el.style.top = `${this.imageHeight}px`
    },
    methods: {
      handlePlaylist(playlist) {
        const bottom = playlist.length > 0 ? '60px' : ''
        this.$refs.list.$el.style.bottom = bottom
        this.$refs.list.refresh()
      },
      scroll(pos) {
        this.scrollY = pos.y
      },
      back() {
        this.$router.back()
      },
      selectItem(item, index) {
        this.selectPlay({
          list: this.songs,
          index
        })
      },
      random() {
        this.randomPlay({
          list: this.songs
        })
      },
      ...mapActions([
        'selectPlay',
        'randomPlay'
      ])
    },
    watch: {
      scrollY(newVal) {
        let translateY = Math.max(this.minTransalteY, newVal)
        let scale = 1
        let zIndex = 0
        let blur = 0
        const percent = Math.abs(newVal / this.imageHeight)
        if (newVal > 0) {
          scale = 1 + percent
          zIndex = 10
        } else {
          blur = Math.min(20, percent * 20)
        }

        this.$refs.layer.style[transform] = `translate3d(0,${translateY}px,0)`
        this.$refs.filter.style[backdrop] = `blur(${blur}px)`
        if (newVal < this.minTransalteY) {
          zIndex = 10
          this.$refs.bgImage.style.paddingTop = 0
          this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
          this.$refs.playBtn.style.display = 'none'
        } else {
          this.$refs.bgImage.style.paddingTop = '70%'
          this.$refs.bgImage.style.height = 0
          this.$refs.playBtn.style.display = ''
        }
        this.$refs.bgImage.style[transform] = `scale(${scale})`
        this.$refs.bgImage.style.zIndex = zIndex
      }
    },
    components: {
      Scroll,
      Loading,
      SongList
    }
  }
</script>

<style scoped lang="less">
  @import "../../common/css/variable.less";
  @import "../../common/css/mixin.less";

  .music-list {
    position: fixed;
    z-index: 100;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    background: @color-background;
    .back {
      position: absolute;
      top: 0;
      left: 6px;
      z-index: 50;
      .icon-back {
        display: block;
        padding: 10px;
        font-size: @font-size-large-x;
        color: @color-theme;
      }
    }
    .title {
      position: absolute;
      top: 0;
      left: 10%;
      z-index: 40;
      width: 80%;
      .no-wrap();
      text-align: center;
      line-height: 40px;
      font-size: @font-size-large;
      color: @color-text;
    }
    .bg-image {
      position: relative;
      width: 100%;
      height: 0;
      padding-top: 70%;
      transform-origin: top;
      background-size: cover;
      .play-wrapper {
        position: absolute;
        bottom: 20px;
        z-index: 50;
        width: 100%;
        .play {
          box-sizing: border-box;
          width: 135px;
          padding: 7px 0;
          margin: 0 auto;
          text-align: center;
          border: 1px solid @color-theme;
          color: @color-theme;
          border-radius: 100px;
          font-size: 0;
          .icon-play {
            display: inline-block;
            vertical-align: middle;
            margin-right: 6px;
            font-size: @font-size-medium-x;
          }
          .text {
            display: inline-block;
            vertical-align: middle;
            font-size: @font-size-small;
          }
        }
      }
      .filter {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
        background: rgba(7, 17, 27, 0.4);
      }
    }
    .bg-layer {
      position: relative;
      height: 100%;
      background: @color-background;
    }
    .list {
      position: fixed;
      top: 0;
      bottom: 0;
      width: 100%;
      background: @color-background;
      .song-list-wrapper {
        padding: 20px 30px;
      }
      .loading-container {
        position: absolute;
        width: 100%;
        top: 50%;
        transform: translateY(-50%);
      }
    }
  }
</style>